This invention relates to the utilization of advantages offered by an economizer cycle to provide effective continuous and gradual variability in the control of multiple operating parameters in a refrigerant system.
Refrigerant systems typically operate to provide heating or cooling for various applications. In a refrigerant cycle of a standard refrigerant system, a compressor compresses a refrigerant. The compressed refrigerant is delivered to a condenser, and from the condenser to an expansion valve. From the expansion valve the refrigerant is delivered to an evaporator, and then back to the compressor.
One way to improve efficiency of modern refrigerant cycles is the use of an economizer cycle. In the economizer cycle, a portion of the refrigerant is tapped downstream of the condenser, and passes through an auxiliary expansion device. Passing this tapped refrigerant through the auxiliary expansion device cools the refrigerant. The main flow of refrigerant is passed through an economizer heat exchanger along with this tapped cold expanded refrigerant. Thus, the main flow is cooled in the heat transfer interaction with this tapped refrigerant flow. This subcooled main refrigerant flow thus has a greater cooling capacity when it reaches the evaporator. A similar process, although generally reversed, can be utilized in heating mode for providing a similar economizer function. For purposes of this application, the invention will be described in a cooling mode, however, a worker of ordinary skill in the art will recognize its parallel application in a heating mode.
Generally, known economizer cycles have either been on or off to vary system capacity. The prior art has utilized a continuous modulation valve, located in the liquid region upstream of the economizer heat exchanger. However, this continuous modulation valve has not been utilized to achieve anything other than a preset superheat value of refrigerant entering the compressor or to flood the compressor with additional liquid refrigerant to cool the compressed vapor within the internal compression process.
The present invention recognizes that the use of an economizer circuit provides the refrigerant circuit designer with a good deal of flexibility and overall system control.